Art of purifying rubber.



EATENTED JUNE 9, 1908.

No. 89o,216. y

H. o. CHUTE. ART 0T PUEIFYTNG RUBBER.

APPLICATION FILED JAN. ll, 1907.

L@ Il.

Poom? amounts or 1mpur1t1es,'th1s being especia y HilltRY O. CHUTE, OFCLEVELAND, OHIO.

ART OF PURIFYING RUBBER.

no. sedere.

Specification ol Letters Patent.

Patented June 9,

, Application led January 11, 1907. Serial No. 351,833.

To all whom 'it may concern:

Be it known that l, HARRY 0. CHUTE, residing at lCleveland, in thecounty. o'f Cuyaboga and State of Ohio,.have invented certain new anduseful improvements in the Art of l'uriying Rubber; and l do herebydeclaro the following to be a full, clear, and exact'description of thesame, such as will enable vothers skilled in the art to which itappertains to make and use the same.

This invention relates to the art of puritying rubber and-consists inramethod of puritying crude rubber and apparatus for performing the same,said method consisting in methodically extracting the various impuritiesof crude rubber by certain compound solvents exercising selective.action upon certain constituents, and used in regulated amounts and in aregulated way, and said apparatus comprising structures adapted to' selectively `extract various im urities from` crude rubber and to performot er like o eretions; all as more fully hereinafter set Iortb and asclaimed.

Crude rubbers, particularly those oi the grades, contain relatively lare true oi the rubbers from the newer sources, such as pontianak, or deadborneo, guayule, Africans, and a number of the "extracted rubbers.Better grade products such as ordinary balata and gutta-percha arealso'apt to be impure. The impurities comprise in addition to water,which occasionali exists in rather large amount and is dil-lieu t toremove, considerable quantities of resin and some fats and eXtractivematters. Extract-- ed rubbers, made by digesting vegetable materialswith hydrocarbon solvents, contain besides the rubbery gum proper,ractically everything which was soluble in tlie original material, andin addition much of the hvdrocarbon employed. Gasolene and nap tha, thesolvents most used, invariabl contain more or less oi the`higher-boiling ydrocar` bons like lubricating oils, and these are apt tostay with the rubber throughout. Hydrocarbons and crude petroleum arealso often used in precipitating latex or in curing the,

precipitate, and'hydrocarbons from these sources are frequenti found incrudmoib extracted commercieI rubbers. In iini'shed rubber goods thesehydrocarbon bodies .are quite detrimental.

The amount of water and resin in some` samples of crude rubber is quitelarge, as for instance inserire samples of crude pontianalr lwhichcontain 6G per cent. water and 30 per cent. resin to only about 10 percent. real rubber, or 1n guayules which contain a tlurdoi their Weight1n resin, waterand other impurities. Some ol this resin is probablytermedA by the oxidation of' the rubbery gums, but much of it isprobably naturally associated with such gums in the plants.

Speaking broadly, in purifying crude rubbers, it is necessary to removewater, resin and injurious hydrocarbons. Water is diflin cult to removeas ythe crude rubber cannot well be heated to any extent withoutinjurious oxidation and such moisture as happens to exist interiorly ofa lump of rubber is el fectually sealed therein. ln itspresencc, few oftheresin solvents act well.

Many solvents have been tried for the pui`- pose of purifyin cruderubber, but they usually have prove objectionable in one way or another.The hydrocarbons while dissolving resin a'nd hydrocarbon impurities alsodissolve some rubber, while they do not con^ (l `tact Wellwith moistrubber. And they usuticularly when used inthe methodical Way hereinafter`set forth.A This compound solvent is miscible with water and dissolvesit out of the crude lrubber. Consequently it -wets or, contacts withthe-rubber very thoroughly, which enables it to reach the s resins. Theresins are veryl soluble-in this com ound solvent, and relatively littleof the atter is therefore requisite to treat much rubber. mixture ofabout equal parts of the two ingredients will dissolve about 20 percent. of resin without dissolving the rubber. or source of the acetoneused is not a matter of indiierencefthe low boiling ketonic bodyextracted from wood spirit and known in commerce under the name ofmethyl ace tone being rather better adapted lor this I have found 'thatthe character.

purpose than ordinary acetone made from` Alone, methyl acetate tends tohydrolyze or' split up with water, especially when heated therewith, asin lractionating it away from water, to re-form the acetic acid andmethyl alcohol from which it was originally made, but in the presenceolacetone or methyl acetone, this tendency disappears. ln treating raw,crude, moist 'rubber of course water inevitably gains access to thesolvent and this protective action is a great advantage.

f The new compound solventreadily dissolves 1- whatever injurioushydrocarbons may be in the rubber.

In use, the rubber may simply be torn or disintegrated in the presenceof the compound solvent described. Water and resin and hydrocarbondissolve, leaving the rubber behind. By now washing the rubber with alittle water, the residual solvent is at once extracted, leaving therubber tree of volatile bodies. From this portion ot' water the solventis readily regained by distillation in condition to serve anew. Asstated, the methyl acetate is protected by the presence ol the othersolventI trom the chemical action of the heated Water in suchdistillation. On l'urther washing the rubber with more water, using anyof the ordinary mills or rolls for this purpose, removal of sticks,

leaves, sand and other mechanical impurities can be accomplished withextraordinary ease, the removal el the-sticky resins leaving the rubberproper with little tendency to cling to foreign bodies. The completenesswith which subsequent mechanical purification can be effected is one ofthe great adyantages of the use of my process.

As stated, ordinary acetone may be substituted for the methyl acetone,either in whole or in part, but I prefer the latter body.

Methyl acetate may also be protected against decomposition with water bythe use of one ofits hydrolyticproducts, namely methyl alcohol. Underthe phase rule, the decome position ordinarily proceeds to a certainbalance between the amount of decomposed and undecomposed material inthe presence el a given amount of water, but decomposition can beprevented as well by the use of a balancing amount of one of thedecomposition products as by both together'. About 10 per cent. ofmethyl alcohol will protect methyl acetate, and the mixture forms aneilicient solvent for present purposes. Ethyl resin.

acetate may be substituted for the methyl ester in admixture withacetone, or ethyl acetate protected by a proper amount of itsdissociation product, namely ethyl alcohol, may also be used. i

ln methodical work, it is better to replace the simple treatmentdescribed by a more systematic treatment eeonomizing solvent by usingthe same portion of solvent successively on 'diil'erent portions otrubber. A

mixtureotl methyl acetate and methyl ace'- tone has considerableatllnity for' water and readily dehydrates rubber. The water-containingsolution so formed however is not as good a solvent for resins as whendry, but after once dissolving resins it will stand some absorption ofwater. In the case of moderately moist rubber therefore a very suitablemethod of operation is to treat the fresh rub-L ber with a portion ofsolvent which has extractedV resin from another'portion. Thisresin-saturated but dry solvent will extract the water without muchprecipitation of The dried rubber may now be treated with fresh drysolvent to extract the resin, and the solution so formed utilized to drymflre rubber prior to its going to the recovery sti In the case et verymoist rubbers, like pontianak, which occasionally contains up to 60 percent. moisture, the procedure is advan tageously still more elaborate,each portion of rubber being treated at least four times, using twoportions of solvent. As stated, water-containing solvent does notdissolve the resin well. Therefore the fresh rubber is treated in twostages to dry it and then in two stages to extract the resin. The freshrubber is first contacted with solvent which has been contacted withanother portion of rubber. This takes out nearly all the water, leavingonly a little in the form of a solvent solution wetting the rubber. Thesolution of solvent and water goes to the still. The solvent-wettedrubber is next treated with a fresh portion otfresh dry solvent toremove the traces of water. The solvent drawn ofi' is used in thefirst-stage proceeding on fresh rubber. The rubber which has been twicetreated is now treated again with a portion of solvent which has oncebefore been used on dry rubber, and the saturatedresin solution formed.is sent to the still. The thrice extracted rubber is now treated oncemore but this time with fresh solvent and the resin solution formed ispassed over dried rubber for the third-stage extraction described. Inthis method of operation it will be seen that the same portion of rubberis treated with two portions of solution in 'Iwo stages for each portionol solvent; it is a four-bath treatment in two series. In the firstseries the water is methodically extracted; in the second series theresin is methodieally extracted. The extract formed in each series goesto the same still and the solvent 1s ing up what resin it will, thisportion is sent to treat another portion of dried rubber and thence tothe kettles.

In the described operation, it will be seen that the rubber has beenfour timestreated with the solvent; once with once-used drying solvent,next with fresh drying solvent, then with once-used resin extractingsolvent and finally with fresh solvent, while two portions of solventhave been used, one portion treating two lots of rubber to extract waterand` then going to the kettle while the other portion treats two lots ofrubber to extract resin and then goes to the kettles. The reason forthis manner of operation is that water-containing solvent is not so-good for extracting resin, neither can resin be Well' extracted frommoist rubber.

'The 4-stage, 2-solvent portion treatment is best adapted to very moistrubber. If the crude rubber is drier, the dehydration can be restricted't"o one stage, the fresh solution.

used being run directly to the kettle without use on another portion ofrubber. It is ordinarily best, however to conduct the resin extractionproper in a plurality of stages to secure the maximum utilization of thesolvent power of the solvent used.

The rubber which has been methodically treated in the manner describedis'now ready for washing. With the water removed as stated, the resin isvery thoroughly extracted, freeing the rubber of its stickiness and bysimple maceration with water it can be thoroughly freed of suchmechanical impurities as sticks, stones, sand, leaves, dirt and thelike. For this purpose water is introduced in the extractor A,A through,17 16 17, 10 and 9. This is best done in two stages, a little waterbeing introduced" and heated to absorb and boil o'f the solvent, whicheseapesthrouvh 6, 7 and 8. More water is then added and the macerationcontinued until the rubber is agwater, dischargediand recharged.V Eachof course in turn becomes theiifth in series.

In the operation of the kettles, two are ordinarily in use while waterand resin are being removed from the third. rIhe water containingsolvent from theiirst two extractions, supposing the 2-stage,.4bathtreatment to be employed, is run into one kettle, say F, while thericher resin solution is run into G, H being out of operation. After thesolution is distilled o'f 'and the resin and liquid from the columnaccumulate therein, water containing solutionis now run into H and soon. Ihe vapors from the kettle which happensto be In the describedmethodical treatment ,l glven the crude rubber, it will be seen that`portions of' solvent withl widely varying qluantitiesof water or ofresinmay be disc iarged into any one ci.' the kettles and the apparatusshown enables a very methodical treatment of these varying liquids.

From the varying liquids stated, th'e columns will produce varyingdistillates and these may be received separately by the variousfsolventtanks, I, J, and K. Pure dry solvent is returned tothe extractors forreuse While less pure or less dry solvent such as may be delivered bycolumn L is returned by way of pipes 31, 17 and 15 toca kettle at theVmoment handling similar liquid, whence its umn M delivering from t erich vapors assed into it, a high-grade dry solvent whi e lowgradecolumn L, concentrating relatively poor vapors tothe same extent,delivers 'a comparatively rich but moist solvent. By use of the twocolumns, complete concentration is rendered practicable, the one neverhandling anything but rich vapors while the otherprepares poorermateriall for its use.

Should the entirecharge in any one kettle be worked in one column aftertlie'solvent was boiled oi from the kettle, the column would have a weaksolution in its chambers, which would render it substantiallyimpossible, with convenient and economical working to form concentratedsolvent from the next charge.'

Assuming that a charge of solvent, water and resin, relatively rich 'insolvent is in F, highrade vapors are first boiled oi'l" 'and sent trough pipe 21 to M for concentration,

the weak liquid from the base of the still be- `which is received in oneof t e solvent tanks for return to' a kettle dealin at ,the moment withrich li uid. After ex austion of the rich vapors om F, column M 1s nextcon- .nected to, say, G, which is temporarily producing rich vapors andso on. y Each kettle continuously Cir 'consists ivater and then treatingwith another alternately communicates with vM and L in handling a freshcharge. Thus M and L are at Work producing solvent of different grade. i

ln case a higher boiling solvent is desired, higher ketones, such asmethyl-propyl lite-v tone, may be substituted for all or part of theacetone or methyl acetone.

l. The process of purifying rubber which consists 1n treating the samewith a compound solvent comprising acetone and methyl acetate.

2. The processl of purifying rubber Which' consists in treating the samewith a compound solvent comprising methyl acetone and methyl acetate.

3. The process of purifying rubber Which consists in treating'the samewith a com pound solvent comprising methyl acetone and an acetic ester.

The process of purifying rubber which consists in treating the same witha compound solvent comprising a ketone and an acetic ester.

, 5. The process of purifying rubber which consists in treating thesaine with a compound solvent comprising acetone and an acetic ester.

6. The process of purifying rubber which consists in treating the samewith a solvent tol remove water and then treating with another portionof a solvent to remove resin.

'7. The process of urifying rubber which consists in treating t le samewith a solvent to remove Water, treating With another portion of7 asolvent to remove resin and macerating in the presence of Water toremove mechanical' impurities.

8. The process of purifying rubber Which in treating the same with asolvent in a plurality of stages to remove Water methodically, andtreating with' another portion of a solvent to remove resin.

9. The processof urifying rubber which consists in treating tlie sameWith a solvent in a plurality of stagesV to remove Water methodically,and treating with another pore tion of a solvent to remove resin in ayplurality of stages.

l0. The process of urifying rubber `which consists in treating t e samewith a compound solvent comprising an acetic ester and a protectivesubstance and thereby removing portion oia solvent to remove resin.

11. The process ofl urifying rubber which consists in treating t e samewith a compound solvent comprising methyl acetate and acetone andthereby removing the WaterI and then treating with .another portion ofthe same'solvent toremove resin.

12. The process of4 urifying rubber'which consists in treating t el sameWith a comdise and returning the pound solvent comprising anacetic esterand a protective substance and thereby removing Water and then treatingwith another portion of the saine solvent to remove resin'.

13. The process of purifying rubber which consists in treating the samewith a portion vof a compound solventconiprising an acetic ester and aprotective substance and thereby dehydrating the same, treating withanother portion of the same solvent to remove resin and inallymacerating with Water to remove mechanical impurities.

14. The process of urifying rubber which consists in treating t e samewith two successive portions of solvent to remove water, and thentreating with a plural-ity of successive portions or solvent to removeresin. y

l5. The process of purifying rubber which consists in dehydrating cruderubber by once-used solvent and removing the Water containing solventfor recovery of solvent, completing the dehydration` by fresh solventand removing the solvent for re-use, extracting the resin from the driedrubber by once used Ysolvent and removing the solution formed forrecovery of solvent, and extracting residual resin b fresh solvent andremovin the solvent tor re-use.

16. e process of purifying rubber which consists in dehyd" "ing cruderubber by once-used solvent l removing the water containing solventrecovery ci solvent, completing the dehydration by fresh solvent andremoving the solvent for re-use, extracting the resin from the driedrubber by once-used solvent and removing the solution 'formed forrecovery of solvent, extracting residual resin by fresh solvent andremoving the solvent for re-use and finally macerating the rubber withWater to remove residual solvent.

f 17.- The process of purifying'rubber which consists in dehydratingcrude rubber by once-used solvent and removing the Water containingsolvent for recovery of solvent, completing the dehydration by freshsolvent and removing the solventfor re-use, extracting the resin fromthe dried rubber by onceused solvent and removing the solution formedforrecovery of solvent, extracting residual resin by lfresh solvent andremoving the solvent for re-use and finally macerating the rubber withWater to remove residual solvent and mechanical impurities.

y 18. The process of treating crude rubber which consists in extractingcrude rubber with successive portions of solvent to dehydrate andextract resin, transmitting the used portions toa common boiling-settle, boiling therein, collecting and concentrating the rst richportions of vapors in a column, storing the rich condensate therefromfor re- Weak vliquid therefrom vto the' kettle, collectiiigandconcentrating succeeding. collecting t e condensate therefrom andreoo'rer vapors in a second colu f ies `turning to a boiling kettle tobe mixed with a. I fresh rich char e, returning the Weak liquid co umnto pass to the solvent tank and that of another to return to thekettles.

20. In a rubber purifying p'lant, the combination of a lurality ofext'ractors, pipe connections ena ing used liquid from any of suchextractors to be returned to any other, pripe' connections enablingintroduction of esh liquid into any of such extractors, a plurality ofdistilling kettles, pipe connections enabling liquid from any extractorto be introduced into any of such kettles, and

fractionating and condensing means ena-A bling the vapors from thekettles to be returned to the extractors in a concentrated dry state. I

21. In a rubber purifying plant, the combination of a plurality ofextractors connected in battery for alternate and successive use, steamheating means and condensing means oneach of said extractors, and astill and pipe connections enabling liq uid'froin the extractors to befractionated and re-.

turned to the extractors.

2.2. In a rubber purifying plant, a plurality of extractors connected inbattery for successive use of a portion of solvent on a plurality ofsamples of rubber,`a common solvent supply tank connected to all theextractors and means for receiving liquid from each of the extractors,recovering solvent therefrom and returning to the solvent supl pluralityof samples of rubber, a source of solvent supply, a solvent pipe havingconnections with each extractor, a plurality of kettles, an exhaustsolvent pipe having valved connections with each extractor vand eachkettle, and fractionating and distilling means having connection witheach kettle and also with the source oi solvent supply.

24. In a rubber purifying plant, aplurality of extractors, means forintroducing fresh solvent into each extractor, means for conveying usedsolvent from any extractor to any other extractor, means for removingand concentrating solvent from any extractor and means for returning theconcentrated solvent to any extractor.

25. In a rubber purifying plant, a plurality of extractors, means forheating and macerating rubbcrin the presence of liquid in eachextractor, means for passing used liquid from any one of the extractorsto any other, means for introducing fresh liquid into each extractor,means for removing and dis# tilling used liquid 'and returning concen4tratecl solvent, and means for introducing water into any of saidextractors.

26. The process of purifying rubber which consists in extracting Waterfrom crude rubber with a solvent, extracting resin with a solvent fromthe so-dried rubber, and ex-

